fix(ui): faster bitcoin sync refresh + unstick ElectrumX loader (B15,B7)

B15: Home system stats (incl. bitcoin sync %) polled every 30s — too slow;
now 10s so sync progress tracks the actual block height more closely.

B7: the ElectrumX sync overlay was gated only on status!=='synced', so if
the status never flips to 'synced' (ElectrumX stale/disconnected) the loader
stuck on top forever. Now the overlay hides and the app iframe loads when
the sync status is stale (fail-open), while still showing during active
indexing. type-check EXIT 0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/production-quality/TRACKER.md

@@ -66,10 +66,10 @@ Browsing trusted/peer nodes in the Cloud tab connects over Tor instead of FIPS (
 
 ## 🟠 APP-SPECIFIC
 
-### B6 — ElectrumX install button missing "Requires Archival Node" gate — TODO
+### B6 — ElectrumX install gate — PARTIAL (pruned-node gate already works; "no node present" half DEFERRED: false-positive risk without UI test, needs package-presence check)
 Show the yellow requirement badge when no full node / only a pruned node is present (reuse existing yellow badge pattern).
 
-### B7 — ElectrumX UI stuck loader on top — TODO
+### B7 — ElectrumX UI stuck loader on top — FIXED (overlay hides + iframe shows when status stale; type-check green). UI-confirm.
 UI renders but a loader sits on top; possibly stale pre-sync screen not clearing.
 
 ### B9 — IndeedHub keeps stopping on nodes — TODO
@@ -81,16 +81,16 @@ Recurring crash ("still" → prior attempts). Check container logs + resource li
 ### B11 — Companion app: "open in external browser" apps don't work — TODO
 Apps meant to open in a new/external browser don't launch from the companion app; need the phone-default-browser request-modal pattern mobile apps use. Relates to v1.7.90 "open in new tab from companion app".
 
-### B12 — Mempool not connecting to Bitcoin on some nodes — TODO
+### B12 — Mempool not connecting — ROOT-CAUSED (stacks.rs:1278 hardcodes CORE_RPC_HOST=bitcoin-knots; fails on bitcoin-core nodes. Fix=dynamic host detect. Backend, medium risk, test .116)
 mempool can't reach the Bitcoin backend on some nodes. Investigate on .116. Check mempool→electrs→bitcoind wiring + deps.
 
 ### B13 — Fedimint UI not applying CSS — TODO
 Actual Fedimint UI (not pre-sync) renders unstyled. Likely asset path / proxy base-href (assets rooted at `/` vs `/app/fedimint/`). PROGRESS: nginx /app/fedimint/ proxies to :8175 with sub_filter for nostr-provider but NO base-href/asset rewrite. Fedimint UI head has no static CSS link in first 1.2KB (likely JS-module-loaded assets rooted at /). NEXT: dump full fedimint HTML + check if assets request /assets/* (which hit the SPA, not :8175). Fix = inject <base href="/app/fedimint/"> via sub_filter OR rebuild app with correct base. Needs deeper per-app look (fresh context ok).
 
-### B15 — Bitcoin UI sync progress lags — TODO
+### B15 — Bitcoin UI sync progress lags — FIXED (Home.vue poll 30s→10s). UI-confirm.
 Bitcoin UI doesn't update its sync progress fast enough even though the console clearly already has the block-height data. Likely a polling-interval / reactive-update gap between the status source and the UI.
 
-### B16 — Bitcoin sync status on Home > System container vanishes — TODO
+### B16 — Bitcoin sync status vanishes — DEFERRED (homeStatus.ts already partly retains last value; safe fix needs UI test to avoid showing stale-as-live; plan in findings)
 The bitcoin sync status in the Home > System container disappears when it should persist/cache and show an "updating" state. Related to B15 (Bitcoin UI sync lag). Likely the status component clears on empty/transitional poll instead of retaining last-known + showing updating.
 
 ### B17 — archipelago.service flaps on boot before starting — TODO